We’ve already written about classifying instances in Python. However, it’s always nice to have a comprehensive list of classifiers and a step-by-step procedure at hand.

**TRAINING THE CLASSIFIER**

We start with simply importing Orange module into Python and loading our data set.

```
>>> import Orange
>>> data = Orange.data.Table("titanic")
```

We are using ‘titanic.tab’ data. You can load any data set you want, but it does have to have a categorical class variable (for numeric targets use regression). Now we want to train our classifier.

```
>>> learner = Orange.classification.LogisticRegressionLearner()
>>> classifier = learner(data)
>>> classifier(data[0])
```

Python returns the index of the value, as usual.

`array[0.]`

To check what’s in the class variable we print:

```
>>>print("Name of the variable: ", data.domain.class_var.name)
>>>print("Class values: ", data.domain.class_var.values)
>>>print("Value of our instance: ", data.domain.class_var.values[0])
Name of the variable: survived
Class values: no, yes
Value of our instance: no
```

**PREDICTIONS**

If you want to get predictions for the entire data set, just give the classifier the entire data set.

```
>>> classifier(data)
array[0, 0, 0, ..., 1, 1, 1]
```

If we want to append predictions to the data table, first use classifier on the data, then create a new domain with an additional meta attribute and finally form a new data table with appended predictions:

```
svm = classifier(data)
new_domain = Orange.data.Domain(data.domain.attributes, data.domain.class_vars, [data.domain.class_var])
table2 = Orange.data.Table(new_domain, data.X, data.Y, svm.reshape(-1, 1))
```

We use .reshape to transform vector data into a reshaped array. Then we print out the data.

`print(table2)`

**PARAMETERS**

Want to use another classifier? The procedure is the same, simply use:

`Orange.classification.<algorithm-name>()`

For most classifiers, you can set a whole range of parameters. Logistic Regression, for example, uses the following:

`learner = Orange.classification.LogisticRegressionLearner(`**penalty**='l2', **dual**=False, **tol**=0.0001, **C**=1.0, **fit_intercept**=True, **intercept_scaling**=1, **class_weight**=None, **random_state**=None, **preprocessors**=None)

To check the parameters for the classifier, use:

```
print(Orange.classification.SVMLearner())
```

**PROBABILITIES**

Another thing you can check with classifiers are the probabilities.

```
classifier(data[0], Orange.classification.Model.ValueProbs)
>>> (array([ 0.]), array([[ 1., 0.]]))
```

The first array is the value for your selected instance (data[0]), while the second array contains probabilities for class values (probability for ‘no’ is 1 and for ‘yes’ 0).

**CLASSIFIERS**

And because we care about you, we’re giving you here a full list of classifier names:

*LogisticRegressionLearner()*

*NaiveBayesLearner()*

*KNNLearner()*

*TreeLearner()*

*MajorityLearner()*

*RandomForestLearner()*

*SVMLearner()*

For other learners, you can find all the parameters and descriptions in the documentation.